Method for synthesis of acrolein from glycerol

Abstract

The invention provides a technology for producing acrolein from glycerol while maintaining high reagent partial pressures, which leads to higher yield. The invention more particularly relates to a method for producing acrolein from glycerol that comprises the intermediate step of forming glycerol and acrolein cyclic acetals.

1. A method for producing acrolein from glycerol, comprising the following steps:
 (a) reacting, in a first reactor, an aqueous glycerol solution with acrolein in the presence of an acid catalyst so as to form cyclic acrolein glycerol acetals, 
 (b) evaporating the stream derived from step (a) at a temperature of between 100° C. and 300° C., 
 (c) passing a gas stream obtained in step (b) over a glycerol dehydration catalyst in a second reactor, so as to produce an acrolein containing stream, 
 (d) separating the acrolein from the acrolein containing stream derived from step (c), a part of the acrolein being recycled to the first reactor of step (a) for production of acetals. 
 
     
     
       2. The method as claimed in  claim 1 , characterized in that the aqueous glycerol solution has a concentration of at least 20% by weight. 
     
     
       3. The method as claimed in  claim 1  or  2 , characterized in that the reaction of step (a) is carried out with an acrolein/glycerol molar ratio ranging from 0.5 to 5. 
     
     
       4. The method as claimed in  claim 1 , characterized in that it further comprises a step of diluting the stream derived from step (a) before step (b). 
     
     
       5. The method as claimed in  claim 1 , characterized in that the temperature of step (b) is between 130° C. and 250° C. 
     
     
       6. The method as claimed in  claim 1 , characterized in that the dehydration catalyst of step (c) is a solid acid catalyst having a Hammett acidity H 0  of less than +2. 
     
     
       7. The method as claimed in  claim 1 , further comprising adding molecular oxygen or a gas containing molecular oxygen in step (c). 
     
     
       8. The method as claimed in  claim 1 , characterized in that step (d) is carried out by partial condensation of water and of heavy products formed during step (c). 
     
     
       9. The method as claimed in  claim 1 , characterized in that it further comprises a step (e) of converting the acrolein from step (d) into acrylic acid, acrylonitrile, or methionine. 
     
     
       10. A method for producing acrolein from aqueous solutions of glycerol, in the gas phase, wherein a mixture of cyclic acrolein glycerol acetals is an intermediate product.